Power consumption is a significant concern in integrated circuits (ICs), and in very high density ICs in particular. Conventional commercial ICs regularly include millions and even billions of transistors, and may consume up to 100 Watts of power. One concern is that the heat generated may destroy the IC itself. For certain ICs, the concern is also about the power to performance ratio: the performance must be guaranteed with respect to the acceptable power consumption level, which depends on the packaging and cooling apparatus.
Related to power consumption is the need for longer battery life in hand-held devices, such as cell phones, personal data assistants (PDA), iPods, etc. Typical battery life for a PC Laptop is about 2 to 3 hours, iPod for up to 10 hours and cell phone may last about 48 hours on stand-by mode. To further extend the battery life for such devices, batteries with more capacity are needed, or power consumption must be better managed.
Certain conventional power measurement devices are coupled to an IC and estimate power consumption by measuring the current used by the IC. Certain such devices are not sufficiently able, however, to provide the needed information quickly due to a latency effect in measuring power consumption off-the-chip. Some commercial central processing units (CPUs) manage power consumption by monitoring the IC chip temperature. This is an extremely low-cost approach as the temperature sensor can be easily made on the silicon, but this approach however, will not provide direct and immediate information on the power consumption. This power management technique therefore, may only roughly control the power usage while providing needed CPU performance.
Certain other CPU chips employ continuous and direct power measurement in dynamic power management (DPM). This technique involves monitoring the voltage drop across a segment of the power supply line on-chip. By simply applying Ohm's law, the current usage and thus the power consumption may be easily calculated. One major problem of such approach however, is that the resistance of a power supply line on-chip varies due to temperature and other environmental factors. The resistance must be measured before the power consumption may be measured.
There continues to be a need, therefore, for improved power consumption monitoring capabilities, and for systems and methods for continuously monitoring power consumption by circuitry that is on the same silicon chip as the circuits being monitored.